A number of cephem compounds belonging to a class of 3-substituted- or unsubstituted-3-cephem-4-carboxylic acids which have a 2-(2-amino-thiazol-4-yl)-2-(substituted or unsubstituted-alkoxyimino)-acetamido group at the 7 position of the cephem nucleus are known. These cephem compounds of this class have high antibacterial activity against Gram-negative bacteria as well as their resistant strains, but they disadvantageously exhibit rather poor antibacterial effects against Gram-positive microorganisms, as described e.g. in the "Antimicrobial Agents and Chemotherapy", 25, 98 (1984).
Besides, these cephem compounds of this class can poorly be absorbed through the digestive tubes when orally administered, and therefore these cephem compounds have been administered exclusively by injection in practice. Accordingly, many efforts have been made to provide new cephem compounds of this class which can exhibit improved absorption or uptake by the digestive tubes upon oral administration.
We, the present inventors, have extensively made our researches to overcome the above drawback of the known cephem compounds of the class as mentioned above. In the course of our researches, we have synthesized a lot of cephem compounds having different 3-substituents, and examined the antibacterial activity and the absorption through the digestive tubes of said 3-substituted cephem compounds as synthetized by us. As a result, we have now found that a class of new cephem compounds (syn-isomer) represented by the formula (I) ##STR2## wherein R.sup.1 is methyl group or carboxymethyl group and R.sup.2 is carboxyl group or a protected carboxy group, have high antibacterial activity not only against Gram-negative bacteria and their resistant strains, but also against Gram-positive bacteria, and that these new cephem compounds can easily be absorbed or uptaken through the digestive tubes when orally administered.